emailoperator with connection, missing config variable support (from_email), prefering airflow.cfg variable

### Apache Airflow version 2.6.0 ### What happened the email operator when used with a connection is hard coded to use the smtp/smtp_mail_from and email/from_email variables from the airflow configuration. this should be adjusted to check if the connection has these vars set and prefer those instead. there is a warning about configuration of email from airflow configuration being unsupported soon, so these config vars need to be supported in connections ### What you think should happen instead if smtp_mail_from and from_email are set in extra_vars on a connection it should prefer those ### How to reproduce setup airflow.cfg with incorrect smtp/smtp_mail_from and email/from_email variables. attempt to override these with variables on an email connection use the emailoperator with the new connection to send an email see that the email was sent with the variables set in airflow.cfg ### Operating System Debian GNU/Linux 11 (bullseye) ### Versions of Apache Airflow Providers _No response_ ### Deployment Docker-Compose ### Deployment details bitnami containers on baremetal debian with docker-compose ### Anything else lines which need to be adjusted to support connection based vars: - https://github.com/apache/airflow/blob/d4dc73416a652a895ada6484d67879a1aad5f0bb/airflow/utils/email.py#L73 - https://github.com/apache/airflow/blob/d4dc73416a652a895ada6484d67879a1aad5f0bb/airflow/utils/email.py#L128 ### Are you willing to submit PR? - [ ] Yes I am willing to submit a PR! ### Code of Conduct - [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)